This invention relates to daytime running lights for automotive vehicles. Daytime running lights (DRL) are presently mandated by law and/or regulation in Canada. In essence, the mandate requires that all automotive vehicles have exterior lamps which illuminate automatically without express affirmative action by the driver of the vehicle whenever the vehicle is in operation. One type of DRL system comprises means for causing the usual headlamps of the vehicle to be energized with a voltage significantly less than rated voltage whenever the vehicle is in operation. Examples of DRL systems of this type are disclosed in commonly assigned U.S. Pat. Nos. 4,949,012 and 5,030,884. By operating the headlamps at a reduced voltage, which by way of example may be one-half rated voltage, an acceptable daytime running indication is given, and the lamp filament life is less significantly affected than if the headlamps were energized at full rated voltage during DRL operation. A feature of known DRL systems provides for DRL to be interrupted whenever the vehicle is idling with the parking brake set and/or the transmission in neutral gear.
At the present time, DRL is not mandated in the United States. However, some truck fleet owners have equipped their newly ordered United States fleet vehicles with DRL systems of the same type presently used to comply with Canadian vehicle requirements. Actual fleet experience with usage of such DRL systems has resulted in two revelations.
The first revelation arises as a consequence of the long-established custom of the driver of a first vehicle signaling the driver of a second vehicle which has just passed the first vehicle in the same direction of travel to indicate that the second vehicle has cleared the first vehicle by a distance sufficient to allow the second vehicle to re-enter the same lane as the first vehicle. This signaling custom, which is sometimes referred to as flashing, is performed by the driver of the first vehicle momentarily turning its headlamps on and off, perhaps even two or three times in succession. Experience with this custom in a vehicle equipped with a DRL system such as those referred to above has revealed that the signaling is not as distinctive, and hence may not be as readily perceived by the driver of the second vehicle, as in the case of a non-DRL-equipped vehicle because the first vehicle's headlamps no longer switch from zero illumination to full illumination, but rather from a level of partial illumination to one of full illumination.
The second revelation arises as a consequence of certain situations where the driver of a DRL-equipped vehicle is required to turn the vehicle headlamps completely off while the vehicle is operating in gear. An example of such a situation is found when a heavy truck or highway tractor-trailer has turned off an expressway, or highway, to enter a weigh scale station where the vehicle is driven onto scales and weighed for compliance with mandated vehicle highway weight limits. Certain tunnels may also have a requirement that vehicles turn their headlamps completely of during through-transit. In situations like these it is impossible for the driver to turn the headlamps completely off because in the case of approaching weigh scales, the vehicle must be driven onto the scales and therefore remain in gear during the approach, and in the case of transit through a tunnel, the vehicle must also obviously remain in gear under power.
While a simple response to the foregoing revelations would be to install an on-off switch which the driver would operate to defeat the DRL system on such occasions, this is not deemed to be acceptable for several reasons. One, it could prevent a new vehicle from being sold in Canada due to possible non-compliance with the DRL mandate in that country; two, the DRL system will remain defeated past the temporary need to do so if the driver forgets to turn the on-off switch back on.
It is toward providing a new and useful convenience feature which responds to the foregoing revelations that the present invention is directed.